1. Field of the Invention
The present invention relates to a printed circuit board and a method of manufacturing the same.
2. Description of the Background Art
Conductor traces are formed as wiring traces on a substrate by a subtractive method or the like in manufacture of a printed circuit board. Portions of the conductor traces are subjected to electrolytic plating, so that connection terminals are formed. Power feeding to the conductor traces is required for the electrolytic plating. Therefore, wiring portions for power feeding (hereinafter referred to as lead wires for plating) that extend from the portions at which the connection terminals are to be formed to one end of the substrate are formed during formation of the conductor traces. Power is fed to the conductor traces through the lead wires for plating.
According to JP 2006-287034 A, for example, in manufacture of a printed circuit board that is called a BGA (Ball Grid Array) used in a semiconductor device, upper surfaces of bonding pads of the conductor traces formed by the subtractive method are subjected to electrolytic nickel plating and electrolytic gold plating, so that the connection terminals are formed.
The lead wires for plating that extend from the bonding pads on the substrate to the one end of the substrate are electrically connected to an external electrode for plating, so that the power feeding is carried out. The upper surfaces of the bonding pads are subjected to the electrolytic nickel plating, and subsequently subjected to the electrolytic gold plating.
In the foregoing method, however, the lead wires for plating, which are unnecessary after the electrolytic plating, remain on the printed circuit board. When an electrical signal is transmitted through the conductor traces while another electronic circuit is connected to the connection terminals of the printed circuit board, the lead wires for plating become stubs branched from transmission lines. Resonance occurs at a particular frequency in such stubs. This causes a particular frequency component of the electrical signal to be attenuated. This may result in disadvantages such as a blunt waveform of the electrical signal.
Removing the lead wires for plating after the electrolytic plating is considered since the lead wires for plating are not necessary after the electrolytic plating. However, a process of removing the lead wires for plating is additionally required, thus leading to an increase in manufacturing cost.